New Book About Chaser, the Border Collie Who Knows a Thousand Words

Chaser: Unlocking the Genius of the Dog Who Knows a Thousand Words is about psychologist John Pilley, his Border Collie, Chaser, and a retirement project that broke new ground in the field of animal cognition. It's also an inspiring story about a man whose curiosity has kept him going well into his 70s.

It's Not a Trick

Teaching a dog a thousand words is obviously a lot of work, but what was maybe even harder was to convince fellow scientists that a dog can understand even one. And if your dog always comes running when you say "cookie," you may wonder, what's wrong with those scientists? Partly it's that there's a long history to fight.

"A common belief that started with Descartes centuries back is that lower animals cannot reason. They're just machines with blood," Pilley says. "That view continues to persist among linguistic scholars who are not aware of the research that's going on with animal psychologists."

But to be fair, scientists are cautious because people have been fooled before. The animal in one famous case has been immortalized in the scientific lexicon: Researchers talk about needing to avoid the "Clever Hans" effect.

Clever Hans was an early 20th-century horse whose trainer believed he could do arithmetic — until a cleverer observer proved that Hans was actually just reading the trainer's body language. The horse, who answered by tapping his foot, had learned to stop when the trainer unconsciously relaxed at the correct number of taps.

Animals are good at picking up on those kinds of clues, so experiments have to carefully exclude them: Does your dog always get a cookie when you're standing in front of that particular cabinet? When you use a certain tone of voice?

So Pilley had to prove, for instance, that Chaser could fetch a toy that he couldn't see, so he couldn't accidentally clue her in by looking at the right object. It also wasn't enough that she understood a word when he spoke — she had to respond correctly to other people, something many of our dogs do not do with words and commands that they seem to know.

Higher Concepts

What made it even harder to convince the scientific community was the kinds of words Pilley taught her. Chaser knows not just proper nouns — say, "bear" for a particular toy — but common nouns as well, like "toy."

"Learning a proper noun is really nothing more than a label for the object," Pilley says. "But when you learn a common noun, you've learned a concept."

Toys like a ball, a rope, a Frisbee and a stuffed bear don't all have a physical quality in common — what defines them is the abstract idea that they're something you play with. Scientists once thought that concepts like this were unique to humans. And, in fact, even human children don't realize at first... that one word like "toy" can refer to many different objects. But Pilley's work with Chaser has shown that a dog can understand this.